Overcurrent Fault Detector

The Overcurrent Fault Detector is designed to monitor electrical current flowing through a system and trigger a response if it crosses a predefined safety threshold. At the front end, the ACS712 current sensor module (5A version) measures the load current and translates it into a proportional analog voltage output. This voltage signal is routed to the input of an LM393 operational amplifier (IC1), which functions as a voltage comparator. Using a potentiometer connected to the comparator, you can establish a precise reference voltage corresponding to your maximum allowable current limit. Under normal operating conditions, the sensor output remains below the threshold set by the potentiometer, keeping the op-amp output in a state that leaves the BC557 PNP transistor (T1) turned off. When an overcurrent condition occurs, the sensor's voltage output exceeds the reference threshold, causing the LM393 output to switch states. This transition biases the BC557 PNP transistor into conduction, energizing the coil of the 5V single-changeover relay (RL1). As the relay trips, it can physically disconnect or switch the connected load. A 1N4007 diode (D1) is placed across the relay coil to safely suppress inductive kickback voltages when the relay turns off, protecting the semiconductor components from damage. LEDs provide visual indication of power and fault status, while onboard resistors and capacitors stabilize the circuit's bias points and filter out high-frequency noise.